Intake and exhaust valves of an engine may be commanded to remain closed over an engine cycle to deactivate one or more engine cylinders. Further, fuel flow may be ceased to the deactivated cylinders. By deactivating selected engine cylinders at low engine load, engine fuel economy may be increased. In one mode of cylinder deactivation, all engine cylinders may be deactivated when a driver releases an accelerator pedal or when driver demand torque is low. The engine may continue to rotate via the vehicle's kinetic energy rotating the engine via the wheels when the cylinders are deactivated. However, pressure in the engine intake manifold may rise when the cylinders are deactivated since air flows from higher atmospheric pressure into lower pressure in the engine intake manifold. If the engine cylinders are reactivated while intake manifold pressure is high, the engine may produce more torque than is desired. Consequently, vehicle drivability may degrade and vehicle fuel economy may be reduced.
The inventors herein have recognized the above-mentioned disadvantages and have developed an engine operating method, comprising: deactivating one or more cylinder poppet valves in a closed state via a controller in response to a deceleration fuel cut off request; and fully closing a throttle via the controller in response to an actual total number of engine cylinder intake events to provide a desired engine intake manifold pressure in response to the deceleration fuel cut off request.
By closing a throttle in response to an actual total number of engine cylinder intake events to provide a desired engine intake manifold pressure, it may be possible to provide the technical result of improving engine torque control and fuel economy during cylinder reactivation. Specifically, the engine intake manifold pressure may be reduced to a desired pressure in response to an actual total number of cylinder intake events immediately following a cylinder deactivation request. The desired pressure may be a pressure at which the engine produces a desired torque when the deactivated cylinders are reactivated and induct air from the engine intake manifold pressure at the desired pressure and a stoichiometric air-fuel ratio. Thus, engine intake manifold pressure may be reduced during cylinder deactivation so that a desired engine torque may be produced by the engine during cylinder reactivation.
The present description may provide several advantages. For example, the approach may reduce driveline torque disturbances. In addition, the approach may provide improve engine fuel consumption since less spark retard may be needed to control engine torque during cylinder reactivation. Further, the approach may provide more consistent cylinder reactivations.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.